[go: up one dir, main page]

WO1996030718A1 - Identification de systeme - Google Patents

Identification de systeme Download PDF

Info

Publication number
WO1996030718A1
WO1996030718A1 PCT/DK1996/000136 DK9600136W WO9630718A1 WO 1996030718 A1 WO1996030718 A1 WO 1996030718A1 DK 9600136 W DK9600136 W DK 9600136W WO 9630718 A1 WO9630718 A1 WO 9630718A1
Authority
WO
WIPO (PCT)
Prior art keywords
objects
positions
parameters
light
measurement
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/DK1996/000136
Other languages
English (en)
Inventor
Bent Herrmann
Preben HJØRNET
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
PIPETECH APS
Original Assignee
PIPETECH APS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by PIPETECH APS filed Critical PIPETECH APS
Priority to AU52705/96A priority Critical patent/AU5270596A/en
Publication of WO1996030718A1 publication Critical patent/WO1996030718A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object

Definitions

  • the present invention relates to a method for identification of a system, comprising measurement of the shape an object considered to be a part of the system, and systems operating according to this method.
  • the present invention relates to methods and systems for accurate determination of parameters of a system, such as a robot, so conveniently that subassemblies of the system can be produced with low tolerances and, thus, at low cost.
  • the present invention relates to methods and systems for determination of geometrical parameters of objects in a large variety of applications, such as in quality control of manufactured objects, alignment of objects during assembly, recognition of objects, classification of objects, determination of positions of objects, calibration of measurement systems, calibration of manipulator systems, such as robots, etc, etc.
  • a position of a specific point of a surface of an object is determined by moving a mechanical device into contact with the point and reading the position of the mechanical device.
  • coordinate measuring machines have linear or angular scales on moving parts to enable read-out of positions of these parts.
  • One class of non-contact measurements is based on optical measurement principles, according to which an object, the geometry of which is to be determined, is illuminated by a light beam, and reflected light from the surface of the object is detected by a light detector, such as a CCD camera. The position of the points of the surface reflecting light is calculated by triangulation.
  • EP 0 452 422 discloses a "shape acquisition system" capable of delivering coordinates of a three-dimensional object. The system is calibrated using a
  • calibration plate of known dimensions having one or more geometrical reliefs.
  • the precise position of the calibration plate in the system need not be known. However, specific parts, i.e. the geometrical reliefs, with a known geometry of the surface of the calibration plate have to be measured during calibration.
  • EP 0 317 768 discloses a "contour measuring apparatus" for measurement of three-dimensional contours of a surface by directing a plurality of individual light beams from point light sources onto the surface of the object to be measured, detecting the reflected beams of light from the surface of the object, and calculating the local radius of curvature of the measured surface at each point of incidence of the individual light beams. The calculation is based on the position, on the light detector (e.g. CCD-chip), of the image of the corresponding point light source.
  • the light detector e.g. CCD-chip
  • a sphere of precisely known geometrical dimensions is used to calibrate the apparatus. Both the object for calibration and objects to be measured have to be mounted in accurately known positions to ensure successful functioning of the apparatus.
  • a calibration object either has to be mounted in a precisely known position relative to the measurement system, or has to comprise reliefs of precisely known dimensions in a precisely known pattern on its surface.
  • a method for identification of a system comprising measurement of the shape of an object which is a part of the system by observing, by means of the system, arbitrary parts of the object, the position of the object being unknown, comparing data representing the surface of the object with a predefined mathematical model of the system including the shape of the object, and based on the comparison, describing, by means of a
  • characteristic geometrical parameters of an object e.g. the outer diameter of a pipe.
  • the known methods and systems require very accurate positioning of the object to be measured in the measuring apparatus or for calibration purposes, knowledge of geometrical dimensions of specific parts of the object that is measured during calibration.
  • the measuring system determines positions of points on the surface of the object along a contour, such as around a circumferential curve on the outer surface of a cylindrical pipe. If the pipe is aligned properly in the measurement apparatus, the
  • circumferential curve will be a circle, the diameter of which is easily determined. However, if the pipe is misaligned, the circumferential curve will change into an ellipsis, whereby uncertainty in the determination of the outer diameter of the pipe is introduced.
  • the requirement of alignment of the object in the measurement system is avoided according to the present invention by exploiting a priory knowledge of the shape of the object to be measured.
  • the outer surface of a cylindrical pipe may be described by two geometrical parameters, the length of the pipe and the outer diameter of the pipe.
  • the outer diameter of the pipe has been determined with a high precision without knowing the position of the pipe in the measurement system and without knowing which points on the surface of the pipe that are measured.
  • the geometry of the object is much more complicated comprising for example a joint surface of the spigot or the socket of a pipe.
  • system identification is defined as determination of a set of parameters describing a system.
  • the system comprises both the measurement system and objects to be measured.
  • the set of parameters consisted of parameters of an object to be
  • any set of parameters of the system may be determined.
  • the set of parameters of the system to be determined during calibration consists of parameters of the measurement system while the geometrical dimensions of the object measured during calibration are known.
  • a simplified calibration of the measurement system after adjustment of the system may comprise
  • An object may comprise several bodies and, correspondingly, the mathematical model may include a set of shapes of bodies forming the object.
  • the bodies forming the object may be interconnected by mechanical structures or may form parts of a larger body, or, the bodies may not be interconnected and, thus, may be moved around independently of each other.
  • the method is applied to systems for positioning of objects.
  • a method and a system is provided for alignment of objects during assembly by determination of the positions of the objects in relation to each other and repositioning, either automatically or manually, the objects into optimized
  • the objects to be aligned may be different parts of the same object, such as two surfaces of a part for a car body that has to be aligned in relation to each other, two surfaces of a bearing that has to be precisely aligned, etc.
  • robots comprising a vision system with mathematical models of specific geometrical structures may calculate the position of such a structure to be able to position another object, such as a tool, or an assembly, etc, accurately in relation to the structure.
  • a non-contact sensor may be inserted into the tool center point of a robot for regular calibration of the robot.
  • the method is applied to systems for classification of objects by defining each class by specific values of a set of geometrical
  • the measurements e.g. a measured contour along the surface of the object.
  • classification is not dependent on the positioning of the object to be classified.
  • One application of this method is within the meat industry, wherein lumps of meat are
  • the method is applied to systems for recognition of objects (A) that resembles the method of classification described in the previous section apart from an additional final step in the recognition method, wherein the determined minimum of the minimum values is compared to a prescribed threshold value and the object (A) is recognized as the object (B)
  • the method is applied to systems for positioning of objects, such as robots, etc, to identify (i.e. calibrate) the system.
  • determination of the shape of a surface may be dismantled from the system so that the system, afterwards, operates solely based on the parameters determined during system identification without being able to determine shape of a surface of an object.
  • shape of an object refers to fundamental geometrical characteristics of the object described by a set of
  • the shape of a pipe may be defined by its inner and outer diameter.
  • Objects of identical shape may be scaled, i.e. the ratios between corresponding parameters of objects of the same shape are identical.
  • the shape of an object may be defined in any way by data that for at least one specific value of the set of geometrical parameters defining the shape of the object unambiguously define points on the surface of the object, such as by mathematical functions, by a set of geometrical parameters, by coordinates defining a set of points on the surface of the object, etc, the coordinates being generated from e.g. a mathematical model, determinations by a measurement system of positions of points on the surface of an object with the given shape, e.g. by a measurement system according to the present invention, a CAD system, scanning of drawings, etc.
  • the object to be measured is observed by the measuring system by measurement of positions of arbitrary points on the surface of the object in relation to a sensor of the system.
  • the position measurements, whereby a position of a point of a surface of an object is determined may be done by moving a mechanical device into contact with the point and reading the position of the mechanical device, e.g. using a coordinate measuring machine having scales on moving parts to enable read-out of positions of these parts.
  • positions of points of the surface of an object is determined by transmitting one or more beams of radiated energy towards the object and
  • the radiated energy may be of any form, such as ultrasound radiation, sound radiation, electromagnetic radiation of any frequency, such as radiation of X-rays, gamma rays,
  • particle radiation such as radiation of electrons, neutrons, alfa-particles, etc.
  • the object to be measured may interact with the radiated energy by reflecting, refracting, diffracting or absorbing energy or by any combination hereof.
  • a detector of X-rays and a source of X-rays are provided.
  • a laser emits a linear light beam towards the object under measurement
  • a video camera with a CCD chip detects light diffusely
  • the positions of the points of the surface of the object reflecting the light beam are determined by triangulation methods.
  • the beam of radiated energy is swept across the surface of the object e.g. by moving the sources or the detectors or the sources and the detectors in fixed positions in relation to each other in relation to the object, by deflecting the beam of radiated energy by a movable
  • deflecting means e.g. a movable mirror, etc, etc.
  • the radiated energy beams may not be of known shapes.
  • a scene with objects may be illuminated by a set of incoherent light sources emitting substantially white light in all directions, such as light bulbs.
  • Two cameras with known positions in relation to each other may be used to determine positions of points of the surfaces of the objects by stereo techniques.
  • Such a system may also be used to track objects as positions of an object may be determinated as a function of time.
  • the determined positions may be used to control a zooming system of another system or the position of another system, such as a robot, a camera, a system according to the present invention, e.g for detailed measurements of the object, for classification of the object, for recognition of the object, etc, etc.
  • a robot could be equipped with a camera positioned close to the tool center point of the robot.
  • the present system may then be used to guide the tool center point to the object with a rough accuracy and then, use the robot's camera to accurately determine the position of parts of the object to be operated upon by the object.
  • more than one object may be tracked and the distance between objects may be monitored for surveillance and control purposes.
  • coherent sets of radiated energy that has interacted with arbitrary parts of the object and directions of the one or more energy beams or movements of the sensors and/or detectors in relation to the object may be detected dependent upon the sweeping method utilized. If more than one detector of radiated energy is used to detect energy from the same points of the surface of an object, the position of the source of the energy or the direction of the beam of radiated energy need not be known as the positions of points of the object interacting with the beam may be determined by stereo techniques based solely on data from two detectors.
  • the movements of detectors or sources of radiated energy, objects to be measured, or components deflecting beams of radiated energy may be performed by e.g. mechanical
  • the measurement system may comprise adjustable parts.
  • an embodiment of the invention described in more detail below comprises a laser source and a CCD camera in a housing that can be rotated about an axis. The distance between the axis of rotation and the housing is adjustable to accommodate measurement of objects of different sizes. Upon adjustment, the system is recalibrated by a system
  • a system according to the present invention comprises one ore more first sensors, the signal output of which contain information about positions (x sm , y sm , z sm ) of one or more points of the surface of an object to be measured. Positions (x sm , y sm , z sm ) measured by a specific first sensor are defined in relation to a coordinate system SM of that first sensor.
  • a system according to the present invention may comprise manipulators for moving one or more of the first sensors. The position of the first sensors moved by the manipulators will then be measured by a set of second
  • the set of variable parameters T sm comprises the position of the first sensor and other variable states of the first sensor influencing
  • the determination of the position of the surface of an object while the set of static parameters P sm comprises fixed parameters of the first sensor influencing determination of the position of the surface of an object.
  • the one or more sensor signals are denoted I sm .
  • a mathematical model for determination of the position (x sm , y sm , z sm ) of a point on the surface of an object based on the first sensor signals I sm and the parameters of the first sensor P sm and T Bm can be described by the following
  • x sm F smx (I sm , T sm , P sm ) (1)
  • y sm F smy (I sm , T sm , P sm ) (2)
  • z sm F smz ( I sm , T sm , P sm ) (3)
  • Coordinates of a position (x sm , y sm , z sm ) determined in relation to a coordinate system of a sensor may be
  • x b F bx (x sm , y sm , z sm , T b , P b )
  • y b F by (x sm , y sm , z sm , T b , P b )
  • z b F bz (x sm , y sm , z sm , T b , P b ) (6)
  • the system comprises an object of a known shape to be
  • the position of the object in relation to the coordinate system B may be described by a mathematical model comprising fixed parameters P q and variable parameters T q , T q being determined by third sensors.
  • y q F qy (x b , y b , z b , T q , P q ) (9)
  • z q F qz (x b , y b , z b , T q , P q ) (10)
  • the term total system identification denotes determination of all fixed parameters of a system, i.e. the set of parameters P sm , P b , and P q .
  • a total system identification comprises the steps of mounting an object with a known shape in an adequate, but not precisely known, position in relation to the measurement system, measuring the surface of the object, e.g. by moving manipulators of the system along suitable paths, while recording coherent sets of I sm , T sm , T b and T q followed by mathematical calculations as described below.
  • the error value defined by (14) is utilized in formation of a so-called error function which expresses the quality of the system identification, i.e. it gives a quantitative measure for how close the selected set of values of parameters P sm , P b and P q of the system are to their true values. A good determination of the parameters will result in a value of the error function close to zero.
  • the value of the error function is non-negative. Any non-negative function of e may be used as the error function C, such as
  • any known parameter estimation algorithm such as Downhill Simplex, Powell's Methods, Conjugate Gradient Methods, Variable Metric Methods, Levenberg-Marquardt Method, etc, may be used to determine the parameters resulting in the minimum value of the error function. It is an important aspect of the present invention that any point on the surface may be measured during system
  • the position of the object need not be known to be able to determine parameters of the system.
  • the system identification described above relates to the coordinate system Q of the object.
  • the system identification described above may as well relate to any coordinate system, such as the B coordinate system, the SM coordinate system, etc.
  • the methods relating to different coordinate systems are similar. It is of course required that transformations of coordinates and functions can be defined for the coordinate system in
  • the accuracy of the determination of parameters by a system identification may be further improved by performing the system identification for two or more different unknown values for one or more of the fixed parameters to be
  • the system identification could be carried out for a plurality of positions of the energy source.
  • the precision of the determination of the remaining fixed parameters not relating to the position of the energy source is increased as these parameters have to fulfil a larger set of requirements.
  • an object to be used for calibration of the measurement system of the system is formed so that the error function utilized for the calibration has one global minimum and no local minima. In this way, the risk that the
  • the estimation algorithm finds a local minimum and interprets it as a global minimum is eliminated.
  • the optimum shape resulting in an error function with one single minimum may differ significantly from the shape of the objects to be measured contrary to known methods and systems, wherein objects with a shape that is similar to the shape of the objects to be measured are used during calibration.
  • the object used to calibrate the laser line scanner for determination of geometrical parameters of pipes are used during calibration.
  • parameters describing distortion in a CCD camera may be included in the
  • a straight line on the object under measurement is imaged on the CCD chip in the camera as a straight line.
  • distortion in the optics of the system and the camera may cause the straight line on the object to be imaged onto a curve on the CCD chip.
  • the deviation of the curve from the desired straight line is determined by parameters describing the distortion of the system.
  • r is the distance of the point x ku , y ku from the optical axis x k0 , y k0 of the optical system:
  • g(r) A 1 r + A 2 r 2 (20)
  • the transformation from x ku , y ku to x k , y k is defined by four parameters P ku : x k0 , y k0 , A 1 and A 2 that are determined by system identification.
  • the parameters P ku described above may be determined independently of the other parts of the measurement system by a system identification performed exclusively on the optical system with the CCD camera. After determination of the parameters P ku , these parameters and the corresponding mathematical model, i.e. equations (17) - (20), can be transferred to any system in which the optical system with the CCD camera is going to be utilized.
  • the accuracy of the method and system can be improved by
  • the intensity in a laser light beam is given by
  • I 0 is the peak intensity at the center of the laser beam
  • r is the distance from the center of the laser beam
  • w 0 is the gaussian beam radius.
  • the center axis of the line is determined with a resolution that is higher than the resolution of the detector.
  • the center of the line of diffuse reflection of light from the surface of the object can be estimated in many other different ways, such as by calculating a weighted average of the detected intensities across the line image, calculating and determining the zero-crossing of the Hilbert
  • the width of the image of the line has to be larger than the resolution of the detector to be able to estimate the center of the line, a width in the range of 5 to 15 times, preferably 8 to 12 times, such as 10 times, the resolution of the detector is presently preferred.
  • the accuracy of the method and system can be further improved when the radiated beam of energy, such as a laser line sheet, intersects the object under measurement along a straight line, such as when a laser light sheet intersects a plane surface of an object.
  • a system based on contact measurements of the surface of an object.
  • the system comprises a cylindrical measurement sensor with a linearly displaceable actuator which is brought into contact with measurement points on the surface of the object under
  • a linear sensor such as a linear potentiometer, provides an electronic signal, such as a voltage, a current, a digital value, etc, which is a function of the position of the linear actuator.
  • each linear actuator is sensed by a linear sensor as described above for the
  • the mathematical model comprises two variable parameters T b : V 1 and V 2 and 14 fixed parameters P b : a b1x , a b1y , a blz, b b1x , b b1y , b b1z , I 1 , a bx , a by , a bz , b bx , b by , b bz , and I 2 .
  • the transformation between the coordinate systems B and Q comprises six fixed parameters P q : a x , a y , a z , b x , b y and b z .
  • a x , a y , and a z are angles of rotation of the B coordinate system in relation to the Q coordinate system.
  • b x , b y and b z is the position of the origin of the Q coordinate system in the B coordinate system.
  • the system is calibrated, i.e. the set of fixed parameters P sm and P b , with the object shown in Fig. 7 and described in more detail below.
  • P sm and P b the set of fixed parameters
  • Methods and systems according to the present invention can be utilized in a large range of systems for a large variety of applications which systems are not intended for determination of geometrical parameters of objects but wherein system identification according to the present invention is applied to calibrate the systems.
  • system identification according to the present invention is applied to calibrate the systems.
  • a number of examples are mentioned below.
  • a robot such as a robot for welding, assembling parts, etc, is provided according to the present invention with a laser line scanner and system identification is utilized to
  • the width of the gap between parts to be welded together may also be determined by system identification and the welding process may be controlled in response to the determined width.
  • boundary surfaces of the eye of a living being comprising a laser line scanner linearly displaceable in a direction substantially perpendicular to the optical axis of the eye under
  • a CCD camera detects light diffusely reflected or light specularly reflected from the various optical boundary surfaces of the eye.
  • the shapes of the boundary surfaces are determined by system identification independent of the position of the eye as described previously. Different kinds of eye diseases may be classified according to relative positions of the optical boundary surfaces. The previously described classification method may then be applied to determine presence or absence of a specific eye disease and if an eye disease is present, the seriousness of the disease may be quantified, e.g. represented by the error value.
  • An X-ray scanner e.g. for scanning of tissue of living beings, scanning of mechanical parts, scanning of weldings, etc, is provided according to the present invention
  • the surface of an object e.g. the surface of a bone of a living being, is determined by measurement of absorption of the X-rays as different materials, e.g. different kinds of tissue of living beings, absorb X-rays differently.
  • the exact positions of the source and detector of the system is determined by a system identification according to the present invention measuring X-ray absorption of an object of known shape and with a known absorption coefficient of X-rays, its position being unknown.
  • An ultrasonic scanner comprising an ultrasonic transducer for radiation and reception of ultrasound pulses.
  • the distance to the object under measurement is determined by the time interval between transmission and reception of the ultrasound pulse and the velocity of the sound waves in the medium through which the waves propagate. Calibration of and measurements by the ultrasonic scanner are performed according to the methods described previously.
  • a laser scanner for scanning of teeth e.g. scanning of drilled holes in teeth to make a filling which matches the hole perfectly
  • the surface of the tooth reflects the light beams and a pattern of light dots on the tooth is generated.
  • the laser scanner further comprises a CCD camera for detection of diffusely reflected light from the tooth and the geometrical parameters of the hole in the tooth are determined according to the method previously described.
  • the method of classification may be applied to classify different kinds of defects of a tooth optionally followed by determination of characteristic geometrical parameters for the kind of defect in question.
  • the resulting parameters may be transferred to another system for
  • a laser scanner for scanning of surfaces of living beings, e.g. the face of a human being, is provided according to the present invention, utilized to evaluate and plan plastic surgery.
  • the system provides visualization of the outcome of different proposals for surgery and the patient may
  • a method according to the present invention is provided for determination of accuracy of a measurement system as a function of the position in relation to the measurement system of the measurement, wherein an object with an
  • accurately known shape is positioned at different positions in relation to the measurement system and a system
  • the error value in each position of the object determined by the system identification represents the measurement accuracy of the measurement system at that position.
  • a system for monitoring changes in a process such as during surface treatment of mechanical parts, machining of
  • a system for measurement of the suspension of wheels on an automobile comprising four laser line scanners, each laser line scanner positioned in a specific corner of a rectangle and determining the position of the rim closest to the scanner in question by the method already described.
  • the positions of the scanners in relation to each other are determined so that the positions of the rims in relation to each other can be determined. Based on the determinations of the positions, the rims are aligned.
  • a system for quality control of patterns and colours comprising a source of white light, a colour CCD camera, a frame grabber and a computer.
  • the system is calibrated with an object having a known pattern of known colours for determination of parameters describing the system geometrically and optically, interpretation of colours included.
  • the description of the calibration object includes values for the colour and the intensity of light reflected from each point on the surface of the object.
  • the calibration is performed by comparing these values of a large number of arbitrary points on the surface of the object with the known values and adjusting the fixed parameters of the systems for the best match of values as described previously.
  • the error value can be defined by wherein ⁇ (x q , y q , z q ) is the known colour distribution of the surface, ⁇ obs is colour measured, I(x q , y q , z q ) is the known intensity distribution of the surface, and I obs is the intensity measured.
  • a system for thermo graphical applications is provided according to the present invention, operating to similar principles as the system for quality control of patterns and colours described above.
  • the system comprises an infrared sensor for sensing of infrared radiation from a body, such as a human being, and processing means adapted to determine the temperatures at specific parts of the body based on the signal values received from the infrared sensor and
  • the system may be applied in the medical field for diagnose purposes.
  • an object used for calibration of a measurement system may be mounted in and dismounted from the system automatically in order to provide automatical calibration of the system, e.g. to provide automatical calibration at regular time intervals.
  • This is particularly useful in systems comprising actuators for automatical positioning of sensors of the system. Upon a repositioning of one or more sensors, the system can be re-calibrated automatically.
  • an object used for calibration of a measurement system may be positioned in the measurement system by manipulator means and removed from the system again after calibration has been terminated.
  • automatical calibration of the system is provided, e.g. to be executed at regular time intervals, upon adjustments of parameters of the system, etc.
  • Fig. 1 illustrates schematically the operating principles of a laser line scanner for determination of geometrical parameters of a joint surface of a pipe
  • Fig. 2 shows front and side views of a laser line scanner
  • Fig. 3 shows details of the laser line scanner sensor head
  • Fig. 4 shows schematically the sensor head of a laser line scanner with corresponding coordinate systems and system parameters
  • Fig. 5 shows a double laser line scanner
  • Fig. 6 shows a laser line scanner for measurements of
  • Fig. 7 shows an object utilized for calibration of a laser line scanner.
  • Fig. 1 shows the principles of operation of a laser line scanner (1).
  • a laser (2) is mounted in a sensor head (3) together with a CCD camera (4).
  • ⁇ n optical system (5) e.g. a cylindrical lens, transforms the light beam from the laser (2) into a thin sheet of laser light (6) which intersects a pipe (7) under measurement along a thin curve (8).
  • Light diffusely reflected (9) from the points on the curve (8) of intersection between the laser light sheet (6) and the pipe (7) is detected by a CCD chip in the CCD camera (4).
  • the position of points on the curve (8) in relation to the CCD camera (4) is calculated from position of points on the image of the curve on the CCD chip.
  • a light filter that mainly transmits light originally emitted from the laser is
  • the diffusely reflected light (9) from the pipe (7) is transmitted to the CCD camera (4) via a precision mirror (10) in order to provide a compact sensor head (3).
  • the sensor head (3) is positioned on an arm (12) and the arm (12) is rotatably mounted on a
  • the pipe (7) to be measured is mounted in relation to the laser line scanner (1) so that the sensor head (3) can be rotated 360° around the joint surface of the pipe (7).
  • An encoder (11) is mounted on the shaft (13) to provide a signal containing information about the angular position of the arm (12).
  • the laser light sheet (6) sweeps the entire surface of the pipe joint.
  • the angle ( ⁇ ) between the arm (12) of the laser line scanner (1) and the sensor head (3) is between 30° and 45°.
  • the laser line scanner may be positioned outside the transportation path of the objects so that special handling equipment to position the objects in the laser line scanner (1) and remove them again after measurement is not needed and thirdly, even when scanning inner surfaces of an object, it is not
  • the coordinates of the recorded points of the joint surface of the pipe (7) are transformed into coordinates of a coordinate system of the pipe aligned with the center axis of the joint surface of the pipe (7).
  • the surface contour of the pipe (7) is now easily calculated in relation to the center axis and is compared to the design specifications of the pipe for quality control purposes.
  • the measured geometry and the reference geometry may be displayed on a monitor and/or a printer and/or be transferred to another system.
  • the geometrical parameters of the reference object may be provided in any suitable way, such as by a CAD system.
  • Fig. 4 shows schematically the sensor head of a laser line scanner with corresponding coordinate systems and system parameters.
  • a mathematical model for the laser line scanner (1) corresponding to the previously described general model (equations (1) - (16)) is described below:
  • the sensor signals I sm as recorded by the frame grabber represent coordinates (x k , y k ) on the CCD chip of points on the image of a light curve (8) on the joint surface of the pipe (7). From the position (x k , y k ) of an image, the
  • the model of the sensor comprises five fixed parameters P sm : G x , G y , L, ⁇ 1 and ⁇ 2 .
  • G x and G y are gains of the CCD camera (4) and the optical system (5) along the x- and y-axis, respectively.
  • L is the distance along the X sm -axis between the virtual laser (22) and the virtual CCD camera (23).
  • ⁇ 1 is the angle between the laser light and the Y sm -axis (not shown).
  • ⁇ 2 is the angle between the laser light and the X sm -axis.
  • the coordinate system B of the measurement system i.e. the laser line scanner
  • the coordinate system B of the measurement system is aligned with the axis of rotation of the arm (12) and the longitudinal axis of the arm (12).
  • ⁇ is the only state variable of variable parameter T b of the system.
  • Coordinates of the coordinate system SM are transformed into coordinates of the coordinate system B by the following equations:
  • this model comprises four fixed parameters P b : x 0 , z 0 , ⁇ and ⁇ .
  • Z 0 and X 0 are distances between the axis of the camera (4) coordinate system SM to the center of the base coordinate system B.
  • ⁇ and ⁇ are the angles of rotation of z-axis and the x-axis, respectively, of the base
  • the transformation between the coordinate systems B and Q comprises six fixed parameters P q : a x , a y ., a z , b x , b y and b z .
  • a x , a y , and a z are angles of rotation of the B coordinate system in relation to the Q coordinate system.
  • b x , b y and b z is the position of the origin of the Q coordinate system in the B coordinate system.
  • an alternative system to the laser line scanner for determination of geometrical parameters of joint surface comprising one or more non-contact distance sensor, such as laser distance sensor based on triangulation. Each of the sensors generates a signal
  • each of the transformations of coordinates from the coordinate systems of the one or more sensors to the coordinate system (B) of the measurement system may derived analogously to the derivations for the laser line scanner described above and each transformation comprises four fixed parameters eta, phi, x 0 and z 0 , i.e. 5 sensors lead to 20 parameters.
  • the transformation from the measurement coordinate system B to the object coordinate system Q is identical to the corresponding transformation of the laser line scanner.
  • the system is calibrated with the same object as the laser line scanner.
  • the laser line scanner described previously may comprise two or more CCD cameras and two or more laser line sources, i.e. lasers with optical systems emitting a laser light sheet.
  • two cameras are mounted at a fixed distance and at an angle in relation to each other so that they receive light from the same volume in space.
  • a laser line source is rotatably positioned between the two cameras.
  • a precision angular encoder for determination of the angular position of the laser line source is provided.
  • the positions of points of the object interacting with the laser light sheet are determined by stereo techniques based on data from the two cameras.
  • the system may be calibrated with the same object as the laser line scanner.
  • the system may be used to track objects as positions of an object may be determinated as a function of time.
  • the determined positions may be used to control the position of another system, such as a robot, a camera, a system according to the present invention, e.g for detailed
  • a robot could be equipped with a camera positioned close to the tool center point of the robot.
  • the present system may then be used to guide the tool center point to the object with a rough accuracy and then, use the robot's camera to accurately determine the position of parts of the object to be operated upon by the robot.
  • more than one object may be tracked and the distance between objects may be monitored for surveillance and control purposes .
  • a mobile version such as a hand-held version of the laser line scanner is provided according to the invention.
  • a laser line source comprising a laser line source, a CCD camera, and a sound source, such as a loudspeaker, a ultrasound source, etc, positioned in a fixed position in relation to the laser line source and the CCD camera.
  • a number of sound detectors such as microphones, ultrasound detectors, etc, preferably three sound detectors, are positioned on a frame in a fixed
  • the sound source transmits sound pulses that are received by the sound detectors on the frame.
  • the position of the mobile scanner in relation to the frame (and the B coordinate system) can be calculated.
  • the signals from the sensors are transmitted to a mobile computer.
  • the transformation from the B coordinate system to the object coordinate system Q and calibration of the system may be done as already described above for the laser line scanner.
  • the velocity of sound may be determined during calibration as a part of the system identification, or, a sound transmitter and a sound receiver positioned at a fixed mutual distance for measurement of the sound velocity may be provided either on the frame or on the scanner head.
  • Fig. 5 shows a double laser line scanner which is applied when the positions of the joint surfaces of the pipe in relation to each other are critical. For example when pipes are pressed through soil, very accurate joint surfaces of the pipes are required to ensure that the pipes stay on the desired track. A skewness of an end surface may prove fatal to the construction of a pipe line pressed through ground.
  • the laser line scanner (14) to the left measures the outer surface of the spigot (15) of the pipe and the laser line scanner (16) to the right measures the inner surface of the socket (17) of the pipe.
  • Each laser line scanner (14, 16) is calibrated individually as described above as is the position of the spigot (15) relative to laser line scanner (14) and the position of the socket (17) relative to laser line scanner (16).
  • a specific calibration object is used for system identification of the entire system comprising both laser line scanners (14, 16) so that the positions of the two scanners (14, 16) in relation to each other are determined. Then, the positions of the spigot (15) relative to the socket (17) is determined and the length of the pipe and the
  • straightness of the pipe may be determined.
  • Fig. 6 shows a laser line scanner (18) for measurements on a pallet (19).
  • the sensor head (20) is
  • ⁇ is the angular displacement of the object under
  • the laser line scanner shown in Fig. 6 is especially useful for measurements on pallets, tyres, rims, rolled rings, etc.
  • the object used during calibration of the laser line scanners described above is shown in Fig. 7. It is seen that the surface of the object comprises a set of plane surfaces for which the lines of intersections between the plane surfaces are parallel. The main purpose of the calibration is to determine
  • the parameters of the calibration object P q are also determined by the calibration.
  • the position of the calibration object need not be known in order to be able to calibrate the measurement system.
  • the shape of the calibration object is designed in such a way that the error function utilized during the calibration has only one minimum as a function of the fixed system parameters to be determined.
  • the equations (36) - (44) above shows that the transformation from the sensor signals I sm to coordinates (x q , y q , z q ) in the coordinate system Q of the object are non-linear.
  • a number of planes between 5 and 7 is
  • the functions g i (y q ) are linear functions of y q .
  • the laser light sheet (6) will intersect the corresponding i'th surface along a straight line and if the quality of the optics (5) of the detection system is sufficiently high to avoid distortion of the image, this line will be imaged on a straight line on the CCD chip of the CCD camera (4).
  • the image on the CCD chip can be pre-processed to compensate for distortion in the optical system (5) to generate data for a straight line.
  • the knowledge that the image is a straight line can be exploited to improve the accuracy of the system. Further, the
  • processing speed can be improved and the number of data entering the algorithms can be reduced.
  • the laser light sheet (6) will intersect the object along a curve consisting of 5 line segments defining four angles between them.
  • the parameters of each line segments are now estimated and the parameters are used as input to the
  • the calibration object shown in Fig. 7 is presently preferred for calibration of laser line scanners.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

La présente invention concerne un procédé d'identification d'un système. Ce procédé consiste à évaluer la forme d'un objet considéré comme une partie du système. L'invention concerne également des systèmes mettant en ÷uvre ce procédé. L'invention s'applique au contrôle de qualité d'objets manufacturés, à l'alignement d'objets pour leur montage, à la reconnaissances d'objets, à la classification d'objets, à la détermination des positions d'objets, à l'étalonnage de systèmes de mesure, à l'étalonnage de systèmes à actionneur, tels que des robots. L'une des principales caractéristiques de l'invention est de permettre la mesure géométrique précise d'un objet, sans que, par rapport au système de mesure, il soit nécessaire de cadrer l'objet à mesurer avec précision. En outre, un objet à étalonner n'a besoin ni d'être exactement cadré par rapport au système de mesure, ni de présenter pendant l'étalonnage sur la surface à mesurer des points spécifiques.
PCT/DK1996/000136 1995-03-30 1996-03-29 Identification de systeme Ceased WO1996030718A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU52705/96A AU5270596A (en) 1995-03-30 1996-03-29 System identification

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DK34795 1995-03-30

Publications (1)

Publication Number Publication Date
WO1996030718A1 true WO1996030718A1 (fr) 1996-10-03

Family

ID=8092500

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DK1996/000136 Ceased WO1996030718A1 (fr) 1995-03-30 1996-03-29 Identification de systeme

Country Status (2)

Country Link
AU (1) AU5270596A (fr)
WO (1) WO1996030718A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7164968B2 (en) 2002-04-05 2007-01-16 The Trustees Of Columbia University In The City Of New York Robotic scrub nurse
US7582377B2 (en) 2001-11-15 2009-09-01 Toyota Jidosha Kabushiki Kaisha Fuel cell and method of assembling the same
WO2011110144A1 (fr) * 2010-03-11 2011-09-15 Salzgitter Mannesmann Line Pipe Gmbh Procédé et dispositif servant à mesurer la géométrie du profil de corps cylindriques
EP2381213A1 (fr) * 2010-04-21 2011-10-26 Aktiebolaget SKF Procédé et dispositif de mesure d'un composant de palier
RU2556310C2 (ru) * 2013-03-29 2015-07-10 Борис Владимирович Скворцов Устройство дистанционного измерения геометрических параметров профильных объектов
EP3184958A1 (fr) * 2015-12-23 2017-06-28 Liebherr-Verzahntechnik GmbH Système de capteur destiné à l'identification de pièces et/ou à la reconnaissance de position de pièces d'une pluralité de pièces dans un support de transport
EP3392607A1 (fr) * 2017-04-18 2018-10-24 United Technologies Corporation Indicateur de hauteur optique de précision

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0222498A2 (fr) * 1985-10-04 1987-05-20 Loughborough Consultants Limited Prises de mesure d'un corps
GB2204397A (en) * 1987-04-30 1988-11-09 Eastman Kodak Co Digital moire profilometry
WO1992008103A1 (fr) * 1990-10-24 1992-05-14 Böhler Gesellschaft M.B.H. Procede et dispositif pour le mesurage opto-electronique d'objets

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0222498A2 (fr) * 1985-10-04 1987-05-20 Loughborough Consultants Limited Prises de mesure d'un corps
GB2204397A (en) * 1987-04-30 1988-11-09 Eastman Kodak Co Digital moire profilometry
WO1992008103A1 (fr) * 1990-10-24 1992-05-14 Böhler Gesellschaft M.B.H. Procede et dispositif pour le mesurage opto-electronique d'objets

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
K. KEMMOTSU, T. KANADE:: "Uncertainty in Object Pose Determination with Three Light-Stripe Range Measurements", PROC. IEEE INT. CONF. ON ROBOTICS AND AUTOMATION, vol. 3, 5 May 1993 (1993-05-05), LOS ALAMITOS, CA, USA, pages 128 - 134, XP000409800 *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7582377B2 (en) 2001-11-15 2009-09-01 Toyota Jidosha Kabushiki Kaisha Fuel cell and method of assembling the same
US7164968B2 (en) 2002-04-05 2007-01-16 The Trustees Of Columbia University In The City Of New York Robotic scrub nurse
WO2011110144A1 (fr) * 2010-03-11 2011-09-15 Salzgitter Mannesmann Line Pipe Gmbh Procédé et dispositif servant à mesurer la géométrie du profil de corps cylindriques
EP2381213A1 (fr) * 2010-04-21 2011-10-26 Aktiebolaget SKF Procédé et dispositif de mesure d'un composant de palier
RU2556310C2 (ru) * 2013-03-29 2015-07-10 Борис Владимирович Скворцов Устройство дистанционного измерения геометрических параметров профильных объектов
EP3184958A1 (fr) * 2015-12-23 2017-06-28 Liebherr-Verzahntechnik GmbH Système de capteur destiné à l'identification de pièces et/ou à la reconnaissance de position de pièces d'une pluralité de pièces dans un support de transport
EP3392607A1 (fr) * 2017-04-18 2018-10-24 United Technologies Corporation Indicateur de hauteur optique de précision
US10274308B2 (en) 2017-04-18 2019-04-30 United Technologies Corporation Precision optical height gauge

Also Published As

Publication number Publication date
AU5270596A (en) 1996-10-16

Similar Documents

Publication Publication Date Title
US5673082A (en) Light-directed ranging system implementing single camera system for telerobotics applications
US9858682B2 (en) Device for optically scanning and measuring an environment
US4791482A (en) Object locating system
CN102448679B (zh) 至少一个物体以高精度定位到空间最终位置的方法和系统
US6825937B1 (en) Device for the contactless three-dimensional measurement of bodies and method for determining a co-ordinate system for measuring point co-ordinates
US20170160077A1 (en) Method of inspecting an object with a vision probe
CN112334760A (zh) 用于在空间中的复杂表面上定位点的方法和设备
CN106338244A (zh) 3d测量机
JP2002090113A (ja) 位置姿勢認識装置
US7502504B2 (en) Three-dimensional visual sensor
US11276198B2 (en) Apparatus for determining dimensional and geometric properties of a measurement object
JP4658318B2 (ja) 物体の位置および回転位置を求める方法
US5363185A (en) Method and apparatus for identifying three-dimensional coordinates and orientation to a robot
WO1994015173A1 (fr) Detecteur de balayage
WO1996030718A1 (fr) Identification de systeme
US20230186437A1 (en) Denoising point clouds
KR100501397B1 (ko) 3차원형상 측정장치
US12442633B2 (en) Position measurement device and position measurement method
Ahlers et al. Stereoscopic vision-an application oriented overview
US20240353346A1 (en) System and method for three-dimensional laser scanning with optical position sensing
JPH0711407B2 (ja) ガラスエッジ検出装置
EP1379833B1 (fr) Methode permettant d'indiquer un point dans un espace de mesure
US20060023223A1 (en) Apparatus and methods for scanning conoscopic holography measurements
JPH0612252B2 (ja) 三次元形状の自動測定方法
JP2899875B2 (ja) 非接触表面粗さ測定方法およびその測定装置

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AL AM AT AT AU BB BG BR BY CA CH CN CZ CZ DE DE DK DK EE EE ES FI FI GB GE HU IS JP KE KG KP KR KZ LK LR LS LT LU LV MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SK TJ TM TR TT UA UG US UZ VN

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): KE LS MW SD SZ UG AT BE CH DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN ML MR NE

DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
121 Ep: the epo has been informed by wipo that ep was designated in this application
WPC Withdrawal of priority claims after completion of the technical preparations for international publication

Free format text: DK

REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

NENP Non-entry into the national phase

Ref country code: CA

122 Ep: pct application non-entry in european phase